Means of cleaning and protecting metal surfaces



Patented Mar. 18, 1930 Umrsn STATES PATENT o aries JAMES C. VIGNOS, F NITRO, WEST "IRGINIA, ASSIGNOR TO THE RUBBER SERVICE LABORATORIES COMPANY, OF AKRON, 0HIO,-A CORPORATION OF OHIO.

MEANS OF OLEANING AND PROTECTING METAL SURFACES No Drawing.

' employed, a relatively small proportion of a metal lost in pickling;

suitable compound or mixture of compounds of the type hereinafter set forth, in order to diminish and substantially inhibit the pitting and roughening of the clean metal surface by the action of the acid thereon.

The invention is particularly applicable for use in the pickling of iron or steel wire, sheets vor other like metallic objects, but is useful and readily adaptable in many other processes, such as for cleaning or freeing iron or steel in any form from rust, oxide or other deposits by means of dilute acids. Thus, the process hereinafter set forthis adaptable to the removal of deposits collect ing within a water or steam circulating or distributing system and also for removing scale, such as boiler scale or the like from sheets and tubes. The preferred type of acid inhibitors may likewise be added to the acid transported in an acid tank car to prevent corrosion of the car by the acid and can likewise be used to diminish excessive corrosion by water in systems employing mine waters.

The inhibitors disclosed are also adapted for use in the acid solution employed in treating mineral oil fractions in petroleum refineries as well as in other industrial applications wherein an acid other than highly concentrated acid is in contact with a metal surface.

Certain objects of the invention are, then, to prevent the pickle liquor from attacking clean portions of the surface of a metal; to obviate overpickling embrittlement and pitting of the articles treated; to prevent the escape of gases, vapors and acid spray from the pickle vat; to minimize the amount of to-increase the efficiency of the pickling operation and to prolong the effective life of the pickling bath and particularly to speed thevpickling operation. Other and further objects of the invention will be apparent from the follow- Application filed November 19, 1927. Serial No. 234,547.

ing description and accompanying examples.

In addition to the sulfuric acid liquor ordinarily employed in the pickling step, the preferred composition for use therewith neccssary to accomplish the various objects set forth, includes a compound or mixture of compounds having the property of lessening or inhibiting the solvent action of the acid employed upon the metal treated. As such inhibitors, the present invention discloses the use of mercaptans, that is compounds containing the C-SH grouping, and preferably those mercaptans wherein the sulph-hydrate group is attached to a carbon atom of a thiazole group, that is, the

group. Derivatives of mercaptans, such as the sulfids, disulfids, thiocyanates, sulfonates and the like as well as reaction products thereof, have also been found effective when employed as inhibitors. Although the preferred class of inhibitors have been used successful ly, if desired they may be employed in con-.

junction with a foaming agent and/or with an organic solvent for the inhibitor.

In the examples hereinafter set forth of the preferred and improved means of carrying out the pickling process, conditions were.

employed which duplicated, so far as possible, those commonly followed in commercial practice, so far as concerned acid concentrations and temperatures employed. The heating of the metallic test strips in the pickling liquor was, however, from three to four times that ordinarily followed in practice for the acid concentrations employed.

Test pieces of steel approximately three inches square were cut from a sheet after the annealing process had been carried out. The steel employed had a carbon content of approximately 0.04%. These pieces were.

. Average Inhibiting compound employed 93 g iron loss EH in gms.

I N o inhibito 0. O0 0. 357 lCth nz 0. 10 0. 055 Ethylene dithio-dibenzo thiazol 0.05 0. 064 Mercapto tolyl thiazole 0. 10 0.019 Mercapto tolyl thiazole 0.05 0. 014 l'lthylene (lithio-dimer'eapto tolyl thiazole I 0.010 0.033 v Ethylene dithio-dimcrcapto tolyl thiazole. I 0.05 0. 040 M ercapto-benzo-thiazole thiocyanate 0.01 0. 110 Mercapto-benzo-thiazole thiocyanate 0.05 0.090 'lhio phenol i 0. 1 0. 051

\ and thlophenol CaHuSH.

perature of from 176 to 185 F. to 0.). For this acid concentration, commercial practice is to pickle at approximately 165 F. (738 C.) for from fifteen to twenty minutes. In all cases, the results were compared with similar tests wherein no inhibitor was employed. The results obtained from one series of tests wherein a number of different mercaptans were tested as inhibitors are as follows:

The inhibiting compounds set forth in the table possess the following chemical structures: I Ethylene dlthlodibenzothiezole Mercapto-tolyl-thlezole CSH S Ethylene dithlodimercaptotolylthiazole HuC N N C-SCHz.CH2SO S v Mereapto-benzo-thiazole-thlacyanete The results given showthat the loss in weight suffered by the iron test pieces when subjected to the pickle liquor containing an inhibitoris very much less than that resulting under similar conditions when no inhibitor is present in the acid bath.

other'series of tests were carried out under the conditions previously described but employing different inhibitors. The results so obtained were as follows:

I but also materially aromatic primary amine,

.' aldol, the resulting product results of the foregoing tests corre-' spond in general to the first group of results set forth and show that mercaptan compounds, and 7 compounds, when used in extremely small quantities in the pickle liquor, greatly decrease the solvent action of the acid upon the articles pickled. Even greater savings could, of course, be realized by the use of greater quantities of the inhibitor. In every case, the test pieces when taken from the pickle solution were clean and bright and particu- The compounds of the type disclosed herein have'also been found to be effective as inhibitors when used .in the form of a sulfonated compouhd, Such compounds were prepared by treating the mercaptan with a suitable proportion of concentrated sulfuric acid and then heating the mixture at from 100 to 150 C. until fumes of sulfur dioxide were no longer evolved. Solvents of the inhibitors may also be employed in the pickle bath if desired.- 'lthus, glycerine C H 011(3), ethylene-glycol O H OH and other materials have been used as solvents in the process set forth. The following tests were carried out in accordance with the before described and the were obtained:

procedure hereinresults set forth Amount Amount of Compound used iron loss Ethylene dibenzo-thiazole sulfonated 0; 01 gms.-- 0. 047 gms. Ethylene dibenzo-thiazole sulfonated- 0. 05 gms..- 0. 05 gins. Ethylene glycol saturated with mercapto benzo-thiazole 0. 85 cc. 0. 029 gms. 1 part mercapto-benzo-thiazole sulfonated with 25 parts 66 B. sulfuric acid 0 5 ms. 0.007 gins. one 0 00 0. 210 gms.

In the pickling process as carried out, it is customary to agitate the pickle liquor. Inasmuch as hydrogen or other gases are at times evolved in quite appreciable volumes duringthe-process, the effectof agitation and gas evolution frequently results in the spat-- tering of droplets of the acid solution. The loss of such acid is avoided and a consequent improvement of conditions in the vicinity of larly free from surface roughness or pitting.

particularly mercapto-thiazole llO- pickling baths results when a material is addedto the acid liquor which forms a persistent foam blanket over the surface thereof.

Such blanket not only servessubstantially to prevent the spatteringfof the acid solution decreases the loss ofgases when hydrochloric acid and the like are employed.

.. It has been found that when the salt of an such as aniline sulfate, acetate and hydrochloride is treated with an aliphatic aldehyde, for example with possesses an appreciable action" as a pickle inhibitor but is particularly effective when employed in conjunction with other inhibitors because of its foam producing qualities. Thus, a series of tests were carried out in the manner hereinbefore described in detail and thefollowing results were thereby obtained:

I v Amount Composition of inhibitor used a of iron use loss None None 0.213 gms. Potassium mercapto-benzo thiezole plus aniline sulphate treated with aldol 0. 05 gms 0.020 gms. Mercepto tolyl thiazole plus aniline sulphate treated with aldol 0.05 gms 0. 018 gins- 10 cc. foamer, 20 cc. 66B. sulphuric acid, 7 a r 20 cc. glycerine, 1 gram mercapto-benzethlezole 0.85 cm... 0.022 gms. 10 ccJoamer, 20 cc. 66 B. sulphuric acid, 20 cc. ethylene glycol, 1 gram mercaptobenzo thiazole 0.85 cc 0.021 ms- 20 cc. foamer, 20 cc. 66 B. sulphuric acid,

1 gram mercapto-henzo-thiazole 0.85 cc- 0.011 gins. 20 cc. foemer, 20 cc. 66 B. sulphuric acid,

20 cc. ethylene glycol, 1 gram mercaptobenzo-thiazole 0. 85 00.... 0.007 21115.

From the results set forth, it is evident that mercaptan compounds and derivatives thereof comprise a class of efiective inhibitors in processes wherein metals are subjected to the action of an acid. Greater inhibiting action has been found to be produced by the use of a larger quantity of the various compounds than that set forth in the examples. It is not, however, necessary to employ an acid solution containing more than 1% by weight of the inhibiting compound. Equally characteristic results were also realized by the use of acids other than sulfuric, such as hydrochloric and nitric acids in the pickling bath and also in the treatment of other metals. Thus, copper,

bronzes, and other alloys-of various metals have been subjected to treatment by a pickle liquor in the presence of one of the preferred type of inhibitors set forth with the result that the loss of metal due to solvent action of the acid thereon was very materially decreased.

The examples hereinbefore set forth are to be understood as illustrative only and not at all limitative of the scope of the invention. Other examples'are apparent to those skilled in the art to which the invention pertains wherein different acid concentrations, times of treatment and temperatures may be employed. The invention is to be considered as limited solely by the following claims wherein the invention is claimed as broadly as is possible in view of the prior art.

What is claimed is:

1. A metal treating compound comprising a highly ionized mineral pickle acid solution containing less than 1% by weightof a sulucts comprising a highly ionized mineral pickle acid, a foaming agent, and a sulfonated mercaptan compound.

4. A'pickling bath for iron and steel prod ucts comprising a highly ionized mineral pickle acid, a foaming agent, a sulfonated mercaptan compound and a solvent for said mercaptan.

5. A pickling bath for iron and steel products comprising sulfuric acid, a foaming agent, a sulfonated mercapto aryl thiazole compound, and an organic hydroxy compound as a solvent for said thiazole compound;

6. A pickling bath for iron and steel prod ucts comprising sulfuric acid, an aldehyde reaction product of the salt of an amine, a sulfonated mercapto -benzo-thiazole compound, and a polyhydroxy alcohol.

7. A pickling bath for iron and steel products comprising sulfuric acid, the aldol re action product of aniline hydrochloride, 2. sulfonated mercapto-benzo-thiazole and. ethylene glycol.

8. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a-small proportion of a sulfonated mercaptan.

9. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a sulfonated mercapto-aryl-thiazole compound.

10. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a foaming agent and a sulfonated mercaptan compound.

11. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a foaming agent, a sulfonated mercaptan compound and a solvent for said mercaptan.

12. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a foaming .agent, a sulfonated mercapto-aryl-thiazole compound and an orfuric acidsolution containing a small proportion of the aldol reaction product of aniline hydrochloride, a sulfonated mercaptobenzo-thiazole and ethylene glycol.

In testimony whereof I hereunto aflix1 my signature.

JAMES C. VIGNOS. 

